This invention relates to a circuit for use in combination with a processor for producing a control signal. The circuit comprises a bar code reader, such as a WAND type bar code reader, for reading a bar code responsive to code illuminating light for producing reflected light and an optical communication receiver for receiving an optical signal. The circuit is selectively controlled by the control signal to produce an output signal.
In a conventional circuit which will later be described a little more in detail, the bar code reader and the optical communication receiver includes in common an optical sensor for converting a combination of the reflected light and the optical signal to an electric signal. When supplied with the reflected light, the optical sensor produces a bar code signal. When supplied with the optical communication signal, the optical sensor produces an electric communication signal. The bar code signal and the electric communication signal are herein referred to collectively as an electric signal.
A low pass filter filters the electric signal to remove a high frequency noise and to produce a low pass filtered signal. A digitizer is connected to the low pass filter for digitizing the low pass filtered signal to produce a digital signal. A serial communication unit is connected to the digitizer for producing the output signal. An interrupt control unit is connected to the digitizer for producing also the output signal. One of the serial communication unit and the interrupt control unit is selectively controlled by the control signal to produce the output signal.
As will later be described more in detail, the conventional circuit is defective in that the optical signal must have a transmission speed which is limited by a cutoff frequency of the low pass filter.